A device and method is proposed for measuring three-dimensional neutron dose distribution in- phantoms on a real-time basis. This method offers the advantages of neutron detectors which are tissue-equivalent and minimize disturbance to neutron scattering within a tissue-equivalent phantom. By proper selection of high vapor-pressure liquid, microsphere (bubble) diameter and the liquid/gel temperature, the proposed instrument can be used to perform neutron dose distributions within intervals over the energy range from 1 keV to 40 MeV. The proposed instrument is expected to provide linear response over the energy ranges from 1 keV to 100 keV and 60 keV to 40 MeV and be capable of accurately recording dose levels as low as 0.01 cGy. The proposed technique allows individual one-dimensional neutron dosimeter rods to be configured into an array suitable for detailed mapping of neutron dose distribution for use in treatment planning.The proposed Phase I program will include experimental verification of accuracy of detection of neutron dose position. The accuracy of predicting position of neutron-induced bubble formation in superheated liquid dispersions using this technique is expected to be within 1-2 mm.